DYK: **The atmosphere contains only about 0.001% of the total volume of water on the planet (about 1.46 x 109 km3). **The rate at which water evaporates into Earth’s atmosphere is about 5.1 x 1017 liters per year.

Weather is affected by the amount of water in the air. Don’t forget transpiration.

Humidity the amount of water vapor (moisture) in the air warm air can hold more moisture

Relative Humidity Relative Humidity (%)=amount of moisture in the air compared to how much moisture the air can hold (100%=saturated) evaporational cooling use psychrometer and chart 2 thing affect RH amount of water vapor temperature—RH decreases as the temperature rises and RH increases as temperature drops

EX: If the dry bulb reads 10°C, and the difference between the wet and dry-bulb thermometers is 8°C, what is the RH? ____%

Condensation gas (water vapor) COOLS and becomes a liquid air must be saturated (RH=100%) Dew Point (measure as class activity—using jar, water, ice and thermometer) temperature where condensation occurs this is the temperature that dew and frost forms and the temperature where fog/clouds form

Humid vs. Dry Air Masses Dry Humid Warm Moist Low density Rising air current Counter clockwise rotation Anti-cyclonic Cool Dry High density Falling air current Clockwise rotation Cyclonic